This invention relates to cleaning of tubing of heat exchangers, such as steam condensers.
It has already been suggested that heat exchanger tubing may be internally cleaned by mounting brush-basket assemblies on the ends of the tubes, and then by flowing water first in one direction and then the other to cause the brushes to traverse the length of the tubes and then return to their original positions. See Heeren et al U.S. Pat. No. 3,319,710.
It has also previously been suggested as in Cleaver et al U.S. Pat. No. 3,973,592 to utilize a four-way valve for purposes of reversing the water flow within the tubes to cause the cleaning brushes to move in both directions within the tubes.
Furthermore, the U.S. Ghormley Pat. No. 3,548,438 has suggested that, in the oil well flowline art, a cleaning pig may be caused to flow through a pipe against the fluid pressure in the pipe by pumping fluid from a separate liquid reservoir tank of limited capacity and manually manipulating a plurality of flow control valves.
Also, spraying cleaning fluid through nozzles or the like and into the ends of the heat exchanger members has also been suggested in the other three patents listed above. In those patents, there is relative movement between the nozzles and the heat exchange members.
The aforementioned four-way valve has found substantial application in connection with cleaning of steam condenser tubing wherein the condenser housing is approximately 30" in diameter. However, recent developments have indicated that condenser housings of up to 16' in diameter are now needed in connection with turbo-generation of electricity. To handle such mammoth condensers, a four-way valve would have to be extremely large and would not be practical.
It is a task of the present invention to provide a heat exchanger tubing cleaning system which not only is as efficient as prior systems, but which also eliminates the need for a four-way valve for brush reversal in either small or very large exchangers.
It is a further task of the invention to eliminate the need for a separate source of fluid when providing a fluid backflow, and to provide an unlimited supply of backflow fluid under pressure.
It is an additional task of the invention to provide a force which propels the brushes through the tubes without imposing any additional requirements on the primary circulating pump for the exchanger, the force being applied either continuously or intermittently as desired.
In accordance with one aspect of the invention, a portion of the main stream of cooling water flowing upstream of or through the heat exchanger housing is reversed in direction and is directed back through the compartmentalized tubes at a higher pressure than said stream. A reverse flow of water is thus created which carries with it the cleaning brushes to move them in one direction through the tubes. The capacity of the main water circulating pump need not be varied.
In accordance with a more specific aspect of the invention, a reverse flow pump is disposed downstream of the tubes and receives water discharged from the tubes for pumping the water and brushes backward thereinto. The water is pumped in a reverse direction and progressively into one group of adjacent tubes at a time. The progression across the face of the tube ends may be continuous or step-by-step. Termination of reverse flow and return of the brushes is automatic.